VR (Virtual Reality) system can be divided into three segments depending on where the computing power resides. On the low end, a VR system consists of a phone-based VR system, where the computing power is in the phone. On the high end, a VR system is a tethered VR system, where the computing power is mainly outside of the Head Mounted Device (HMD). In the middle, a VR system is All-in-one VR system, where the computing power is within the HMD.
From imaging perspective, a VR system generates a magnified virtual image through imaging optics and either one or two discrete near to eye displays.
Displays for such VR and other computing systems often include panel driving logic. The panel driving logic generally involves display timing controller (TCOM) and row (gate) and column (source) drivers. The TCON receives pixel data from the source such as, for example, a System-on-Chip (SoC), and then controls row and column drivers. The rows are commonly turned on one by one from top to bottom while the data for each row is sent by the source driver. In mobile displays, the functions of source driver and the TCON are often combined and such architecture is referred to as a TCON Embedded Driver (TED).
Motion to photon (M2P) latency is the length of time between the user movement input to full display pixel update to reflect the associated change. Studies have shown low motion-to-photon (<20 ms) latency is necessary to convince an individual's mind that they are in the simulated virtual world (Presence). High motion-to-photon latency can cause motion sickness and nausea. The whole process chain from sensor input to graphics rendering to display contribute to the M2P latency. Current approach of reducing display latency is through higher (90 Hz or higher) than traditional refresh rate (60 Hz). Higher display refresh rate requires higher pixel clock support from both the component providing the display data and the display panel.
For phone-based VR systems, the VR display is the phone display—and hence it is a one-display option. Today such phone displays only have one source driver or TED and it is often placed at the short edge in order to have thin borders at the two long edges. In this case, the left and right eye images are not synchronized since the rows are scanned from left to right direction. Studies have shown this update delay between left and right eye causes discomfort.
All-in-one VR and tethered VR systems often use two discrete displays. In such system, further reduction of the display scanning time is desired since it helps reduce display latency for Organic Light Emitting Display (OLED)-based VR panel solution. Liquid Crystal Display (LCD)-based panels are also considered for VR application, but LCDs have the challenge on slow response time to meet the requirement on low persistence and low latency.